JP2022113238A - Image capturing lens - Google Patents

Abstract

To provide an image capturing lens which satisfies a requirement of a low F-number, and yet offers good optical characteristics.SOLUTION: An image capturing lens of the present invention consists of a first lens L1 having positive refractive power, a second lens L2, a third lens L3, and a fourth lens L4 arranged in an order from an object side to an image side, where the first lens L1 has an object-side surface that is convex near an optical axis and the third lens L3 has an image-side surface that is concave near the optical axis. The image capturing lens satisfies predetermined conditional expressions.SELECTED DRAWING: Figure 1

Description

The present invention relates to an imaging lens that forms an image of a subject on a solid-state imaging device such as a CCD sensor or a C-MOS sensor used in an imaging device.

2. Description of the Related Art In recent years, camera functions have come to be installed in various products such as home electric appliances, information terminal equipment, and automobiles. In the future, it is thought that the development of various products that combine camera functions will progress.

Imaging lenses installed in such devices are required to have high resolution performance while being compact.

As a conventional image pickup lens aiming at high performance, for example, an image pickup lens as disclosed in Patent Document 1 below is known.

In Patent Document 1, in order from the object side, a positive meniscus first lens with a convex surface facing the object side, a biconcave second lens, an aperture stop, a biconvex third lens, and a concave surface facing the object side. The thickness of the entire image reading lens system, the distance between the third lens and the fourth lens on the optical axis, and the thickness of the entire image reading lens system satisfy certain conditions. An imaging lens configured to satisfy is disclosed.

JP 2008-275783 A

When trying to achieve a low F-number with the lens configuration described in Patent Document 1, it is extremely difficult to correct aberrations in the peripheral portion, and good optical performance cannot be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an imaging lens that satisfies the demand for a low F-number in a well-balanced manner and has high resolving power in which various aberrations are satisfactorily corrected. and

Further, with respect to the terms used in the present invention, the convex, concave, and plane surfaces of the lens are defined to refer to the paraxial shape. Refractive power is defined to refer to paraxial power. A pole is defined as a point on an aspherical surface other than the optical axis where the tangent plane perpendicularly intersects the optical axis. The optical total length is defined as the distance on the optical axis from the object-side surface of the optical element positioned closest to the object to the imaging plane. The total optical length and the back focus are distances obtained by converting the thickness of the IR cut filter, cover glass, etc., placed between the imaging lens and the imaging surface into air.

An imaging lens according to the present invention comprises a first lens having a positive refractive power, a second lens, a third lens, and a fourth lens arranged in order from an object side to an image side, and The first lens has a convex surface on the object side in the paraxial direction, and the third lens has a concave surface on the image side in the paraxial direction.

The image pickup lens having the above configuration achieves a low profile due to the positive refractive power of the first lens. In addition, spherical aberration, coma, astigmatism, curvature of field, and distortion are suppressed by making the paraxial convex surface on the object side. In addition, astigmatism, curvature of field, and distortion can be satisfactorily corrected by forming the paraxially concave surface of the third lens on the image side.

In the imaging lens having the above configuration, the refractive power of each lens is arranged in order from the object side: the first lens is positive, the second lens is negative, the third lens is positive, and the fourth lens is negative. Including configuration.

In the imaging lens having the above configuration, the refractive powers of the respective lenses are arranged such that the first lens is positive, the second lens is positive, the third lens is negative, and the fourth lens is positive, in order from the object side. 2 configuration.

In the above first configuration, it is desirable that the first lens has a paraxial biconvex shape. By making the first lens biconvex in the paraxial direction, the positive refractive power of both surfaces is used to reduce the height and suppress spherical aberration, coma, astigmatism, curvature of field, and distortion.

In the first configuration, it is desirable that the second lens has a paraxial biconcave shape. Chromatic aberration, coma aberration, astigmatism, curvature of field, and distortion aberration can be satisfactorily corrected by forming the second lens in a paraxial biconcave shape.

In the first configuration, it is desirable that the third lens has a meniscus shape with a concave surface on the image side in the paraxial direction. Spherical aberration, coma aberration, astigmatism, curvature of field, and distortion can be satisfactorily corrected by forming the third lens in a paraxial meniscus shape with a concave surface on the image side.

In the first configuration, the fourth lens preferably has a meniscus shape with a paraxial convex surface on the image side. Chromatic aberration, coma aberration, astigmatism, curvature of field, and distortion can be satisfactorily corrected by forming the fourth lens in a paraxial meniscus shape with a convex surface on the image side.

That is, in the first configuration in which the arrangement of refractive power is positive, negative, positive, and negative in order from the object side, the shape of each lens is a biconvex shape and a biconcave shape in order from the object side on the paraxial axis. It is desirable to form a meniscus shape with a concave surface on the image side and a meniscus shape with a convex surface on the image side.

In the second configuration, it is desirable that the first lens is paraxial and has a meniscus shape with a convex surface on the object side. Spherical aberration, coma aberration, astigmatism, curvature of field, and distortion are suppressed by forming the first lens in a paraxial meniscus shape with a convex surface on the object side. In addition, by forming a paraxially concave surface on the image side, spherical aberration, coma, and astigmatism can be corrected more satisfactorily.

In the above second configuration, it is desirable that the second lens has a paraxial biconvex shape. The paraxial biconvex shape of the second lens allows positive refractive power on both sides to reduce the height and to correct spherical aberration, coma, astigmatism, curvature of field, and distortion. do.

In the second configuration, it is desirable that the third lens has a paraxial biconcave shape. Chromatic aberration, coma aberration, astigmatism, curvature of field, and distortion aberration can be satisfactorily corrected by forming the third lens in a paraxial biconcave shape.

In the second configuration, the fourth lens preferably has a meniscus shape with a concave surface on the image side. Coma aberration, astigmatism, curvature of field, and distortion can be satisfactorily corrected by forming the fourth lens in a paraxial meniscus shape with a concave surface on the image side.

That is, in the second configuration in which the refractive power arrangement is positive, positive, negative, and positive in order from the object side, the shape of each lens is a meniscus shape with a convex surface on the object side, in order from the object side on the paraxial axis. A biconvex shape, a biconcave shape, or a meniscus shape with a concave surface on the image side is desirable.

It is desirable that each lens surface in the first configuration and the second configuration be formed as an aspherical surface. By forming an appropriate aspherical surface on each lens surface, various aberrations can be better corrected.

The imaging lens of the present invention achieves an F number of 4.0 or less by adopting the above-described configuration.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (1).
(1) 13<νd4<34
However, νd4 is the Abbe number for the d-line of the fourth lens.

Satisfying the range of conditional expression (1) enables good correction of chromatic aberration.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (2).
(2) 0.3<νd3/νd4<2.0
νd3 is the Abbe number for the d-line of the third lens, and νd4 is the Abbe number for the d-line of the fourth lens.

Satisfying the range of conditional expression (2) enables good correction of chromatic aberration.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (3).
(3) 0.25<|r2/r3|<0.85
where r2 is the paraxial radius of curvature of the image-side surface of the first lens, and r3 is the paraxial radius of curvature of the object-side surface of the second lens.

By satisfying the range of conditional expression (3), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (4).
(4) 0.85<|f4|/f<3.85
However, f4 is the focal length of the fourth lens, and f is the focal length of the entire imaging lens system.

Satisfying the range of conditional expression (4) enables good correction of coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (5).
(5) 0.15<|r2|/f<0.55
However, r2 is the paraxial radius of curvature of the image-side surface of the first lens, and f is the focal length of the entire imaging lens system.

By satisfying the range of conditional expression (5), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Further, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (6).
(6) 0.2<|r3|/f<1.2
However, r3 is the paraxial radius of curvature of the object-side surface of the second lens, and f is the focal length of the entire imaging lens system.

Satisfying the range of conditional expression (6) enables good correction of astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (7).
(7) 0.5<r6/|f3|<6.0
However, r6 is the paraxial radius of curvature of the image-side surface of the third lens, and f3 is the focal length of the third lens.

By satisfying the range of conditional expression (7), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (8).
(8) 9<(D3/|f3|)×100<43
However, D3 is the thickness of the third lens on the optical axis, and f3 is the focal length of the third lens.

Satisfying the range of conditional expression (8) makes it possible to reduce the height and to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Further, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (9).
(9) 0.1<|f2|/f<0.7
However, f2 is the focal length of the second lens, and f is the focal length of the entire imaging lens system.

Satisfying the range of conditional expression (9) enables good correction of coma, astigmatism, curvature of field, and distortion.

Further, it is preferable that the imaging lens having the above configuration satisfy the following conditional expression (10).
(10) 0.1<|f3|/f<0.8
However, f3 is the focal length of the third lens, and f is the focal length of the entire imaging lens system.

By satisfying the range of conditional expression (10), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (11).
(11) 13<νd3<34
However, νd3 is the Abbe number for the d-line of the third lens.

Satisfying the range of conditional expression (11) enables good correction of chromatic aberration.

Further, it is preferable that the imaging lens having the above configuration satisfy the following conditional expression (12).
(12) 0.1<r1/f<0.4
However, r1 is the paraxial radius of curvature of the object-side surface of the first lens, and f is the focal length of the entire imaging lens system.

By satisfying the range of conditional expression (12), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (13).
(13) 0.3<r1/|r2|<1.5
where r1 is the paraxial radius of curvature of the object-side surface of the first lens, and r2 is the paraxial radius of curvature of the image-side surface of the first lens.

By satisfying the range of conditional expression (13), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (14).
(14) 0.2<|r2/r8|<1.8
However, r2 is the paraxial radius of curvature of the image side surface of the first lens, and r8 is the paraxial radius of curvature of the image side surface of the fourth lens.

By satisfying the range of conditional expression (14), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (15).
(15) 0.05<|r2/f1|<2.00
However, r2 is the paraxial radius of curvature of the image-side surface of the first lens, and f1 is the focal length of the first lens.

By satisfying the range of conditional expression (15), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is preferable that the imaging lens having the above configuration satisfy the following conditional expression (16).
(16) 0.65<|r3/r7|<3.70
However, r3 is the paraxial radius of curvature of the object side surface of the second lens, and r7 is the paraxial radius of curvature of the object side surface of the fourth lens.

Satisfying the range of conditional expression (16) enables good correction of coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (17).
(17) 0.25<|r5|/f<0.80
However, r5 is the paraxial radius of curvature of the object-side surface of the third lens, and f is the focal length of the entire imaging lens system.

By satisfying the range of conditional expression (17), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (18).
(18) 0.5<|r5|/T3<9.0
where r5 is the paraxial radius of curvature of the object-side surface of the third lens, and T3 is the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens.

Satisfying the range of conditional expression (18) makes it possible to reduce the height and to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (19).
(19) 0.05<|r5|/r6<1.60
However, r5 is the paraxial radius of curvature of the object-side surface of the third lens, and r6 is the paraxial radius of curvature of the image-side surface of the third lens.

By satisfying the range of conditional expression (19), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens configured as described above satisfies the following conditional expression (20).
(20) 0.2<|r5/f3|<2.0
However, r5 is the paraxial radius of curvature of the object-side surface of the third lens, and f3 is the focal length of the third lens.

By satisfying the range of conditional expression (20), it is possible to satisfactorily correct spherical aberration, coma, astigmatism, curvature of field, and distortion.

Further, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (21).
(21) 0.2<r6/f<3.0
However, r6 is the paraxial radius of curvature of the image-side surface of the third lens, and f is the focal length of the entire imaging lens system.

Satisfying the range of conditional expression (21) enables good correction of astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (22).
(22) 0.1<|r7|/f<0.8
However, r7 is the paraxial radius of curvature of the object-side surface of the fourth lens, and f is the focal length of the entire imaging lens system.

Satisfying the range of conditional expression (22) enables good correction of coma, astigmatism, and distortion.

Further, in the imaging lens having the above configuration, it is desirable to satisfy the following conditional expression (23).
(23) 0.2<|r7|/(T3+bf)<1.7
where r7 is the paraxial radius of curvature of the object-side surface of the fourth lens, T3 is the distance on the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens, and bf is the back focus. be.

Satisfying the range of conditional expression (23) makes it possible to reduce the height and to correct coma, astigmatism, and distortion.

Moreover, it is desirable that the imaging lens having the above configuration satisfy the following conditional expression (24).
(24) 0.1<|r7/r8|<1.6
However, r7 is the paraxial radius of curvature of the object side surface of the fourth lens, and r8 is the paraxial radius of curvature of the image side surface of the fourth lens.

Satisfying the range of conditional expression (24) enables good correction of coma, astigmatism, curvature of field, and distortion.

Moreover, it is desirable that the imaging lens configured as described above satisfies the following conditional expression (25).
(25) 6<(D2/|f2|)×100<61
However, D2 is the thickness of the second lens on the optical axis, and f2 is the focal length of the second lens.

Satisfying the range of conditional expression (25) makes it possible to reduce the height and to satisfactorily correct coma, astigmatism, curvature of field, and distortion.

Further, it is preferable that the imaging lens having the above configuration satisfy the following conditional expression (26).
(26) 0.05<|f2/f4|<0.75
However, f2 is the focal length of the second lens, and f4 is the focal length of the fourth lens.

Satisfying the range of conditional expression (26) enables good correction of coma, astigmatism, curvature of field, and distortion.

According to the present invention, it is possible to obtain an imaging lens with high resolving power in which various aberrations are satisfactorily corrected.

1 is a diagram showing a schematic configuration of an imaging lens of Example 1, which is a first embodiment of the present invention; FIG. FIG. 4 is a diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of Example 1, which is the first embodiment of the present invention; It is a figure which shows the schematic structure of the imaging lens of Example 2 which is 2nd Embodiment of this invention. FIG. 10 is a diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of Example 2, which is the second embodiment of the present invention; It is a figure which shows the schematic structure of the imaging lens of Example 3 which is 2nd Embodiment of this invention. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration of the imaging lens of Example 3 which is 2nd Embodiment of this invention. FIG. 10 is a diagram showing a schematic configuration of an imaging lens of Example 4, which is a second embodiment of the present invention; FIG. 10 is a diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of Example 4, which is the second embodiment of the present invention; It is a figure which shows the schematic structure of the imaging lens of Example 5 which is 2nd Embodiment of this invention. FIG. 10 is a diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of Example 5, which is the second embodiment of the present invention; It is a figure which shows the schematic structure of the imaging lens of Example 6 which is 2nd Embodiment of this invention. FIG. 10 is a diagram showing spherical aberration, astigmatism, and distortion of the imaging lens of Example 6, which is the second embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration diagram of an imaging lens according to Example 1 of the first embodiment of the present invention. 3, 5, 7, 9, and 11 are schematic configuration diagrams of imaging lenses according to Examples 2 to 6 of the second embodiment of the present invention, respectively.

As shown in the schematic configuration diagram, the imaging lens according to the present invention includes a first lens L1 having positive refractive power, a second lens L2, and a third lens L3, which are arranged in order from the object side to the image side. and a fourth lens L4. The first lens L1 has a convex surface on the object side in the paraxial direction, and the third lens L3 has a concave surface on the image side in the paraxial direction.

A filter IR such as an infrared cut filter or cover glass is arranged between the fourth lens L4 and the imaging surface IMG (that is, the imaging surface of the imaging element). Note that this filter IR can be omitted.

Since the aperture diaphragm ST is arranged on the object side of the first lens L1, it facilitates the correction of various aberrations and facilitates the control of the angle at which light rays of high image height enter the image sensor. .

[First embodiment]
A first embodiment of the present invention will be described in detail below with reference to FIG.

The first lens L1 has a positive refractive power and is paraxially biconvex. Therefore, the positive refracting power of both surfaces is used to reduce the height and suppress spherical aberration, coma aberration, astigmatism, curvature of field, and distortion.

The second lens L2 has negative refractive power and is paraxially biconcave. Therefore, chromatic aberration, coma aberration, astigmatism, curvature of field, and distortion are well corrected.

The third lens L3 has a positive refractive power and is paraxial and has a meniscus shape with a concave surface on the image side. Therefore, spherical aberration, coma aberration, astigmatism, curvature of field, and distortion are well corrected.

The fourth lens L4 has a negative refractive power and is paraxial and has a meniscus shape with a convex surface on the image side. Therefore, chromatic aberration, coma aberration, astigmatism, curvature of field, and distortion are well corrected.

[Second embodiment]
A second embodiment of the present invention will be described in detail below with reference to FIG.

The first lens L1 has a positive refractive power and has a meniscus shape with a convex surface on the object side. Therefore, spherical aberration, coma, astigmatism, curvature of field, and distortion are suppressed. In addition, by forming a paraxially concave surface on the image side, spherical aberration, coma, and astigmatism can be corrected more satisfactorily.

The second lens L2 has a positive refractive power and is paraxially biconvex. Therefore, spherical aberration, coma aberration, astigmatism, curvature of field, and distortion are well corrected.

The third lens L3 has negative refractive power and is paraxially biconcave. Therefore, chromatic aberration, coma aberration, astigmatism, curvature of field, and distortion are well corrected.

The fourth lens L4 has a positive refractive power and is paraxial and has a meniscus shape with a concave surface on the image side. Therefore, coma aberration, astigmatism, curvature of field, and distortion are well corrected.

In the imaging lens according to the present embodiment, it is preferable that each of the first lens L1 to the fourth lens L4 is composed of a single lens. A single-lens configuration can make extensive use of aspherical surfaces. In this embodiment, by forming appropriate aspherical surfaces on all lens surfaces, various aberrations are satisfactorily corrected. Moreover, since the number of man-hours can be reduced as compared with the case of adopting a cemented lens, it is possible to manufacture at low cost.

In addition, although it is desirable that all lens surfaces of the imaging lens according to the present embodiment are aspherical surfaces, spherical surfaces that are easy to manufacture may be adopted depending on the required performance.

The imaging lens according to the present embodiment exhibits favorable effects by satisfying the following conditional expressions (1) to (26).
(1) 13<νd4<34
(2) 0.3<νd3/νd4<2.0
(3) 0.25<|r2/r3|<0.85
(4) 0.85<|f4|/f<3.85
(5) 0.15<|r2|/f<0.55
(6) 0.2<|r3|/f<1.2
(7) 0.5<r6/|f3|<6.0
(8) 9<(D3/|f3|)×100<43
(9) 0.1<|f2|/f<0.7
(10) 0.1<|f3|/f<0.8
(11) 13<νd3<34
(12) 0.1<r1/f<0.4
(13) 0.3<r1/|r2|<1.5
(14) 0.2<|r2/r8|<1.8
(15) 0.05<|r2/f1|<2.00
(16) 0.65<|r3/r7|<3.70
(17) 0.25<|r5|/f<0.80
(18) 0.5<|r5|/T3<9.0
(19) 0.05<|r5|/r6<1.60
(20) 0.2<|r5/f3|<2.0
(21) 0.2<r6/f<3.0
(22) 0.1<|r7|/f<0.8
(23) 0.2<|r7|/(T3+bf)<1.7
(24) 0.1<|r7/r8|<1.6
(25) 6<(D2/|f2|)×100<61
(26) 0.05<|f2/f4|<0.75
however,
νd3: Abbe number for the d-line of the third lens L3 νd4: Abbe number for the d-line of the fourth lens L4 D2: Thickness on the optical axis X of the second lens L2 D3: On the optical axis X of the third lens L3 thickness T3: distance on the optical axis X from the image-side surface of the third lens L3 to the object-side surface of the fifth lens L5 bf: back focus f: focal length f1 of the imaging lens system: first lens L1 focal length f2: focal length f3 of the second lens L2: focal length f4 of the third lens L3: focal length r1 of the fourth lens L4: paraxial curvature radius r2 of the object-side surface of the first lens L1: the first Paraxial curvature radius r3 of the image side surface of the lens L1: Paraxial curvature radius r5 of the object side surface of the second lens L2: Paraxial curvature radius r6 of the object side surface of the third lens L3: Third lens L3 paraxial radius of curvature r7 of the image-side surface of the fourth lens L4: paraxial radius of curvature r8 of the object-side surface of the fourth lens L4: paraxial radius of curvature of the image-side surface of the fourth lens L4. It is not necessary to satisfy all the conditional expressions, and by satisfying each conditional expression independently, the effect corresponding to each conditional expression can be obtained.

Further, the imaging lens of the present embodiment exhibits more favorable effects by satisfying the following conditional expressions (1a) to (26a).
(1a) 16<νd4<29
(2a) 0.6<νd3/νd4<1.7
(3a) 0.4<|r2/r3|<0.8
(4a) 1.0<|f4|/f<3.4
(5a) 0.25<|r2|/f<0.45
(6a) 0.3<|r3|/f<0.9
(7a) 0.9<r6/|f3|<4.9
(8a) 14<(D3/|f3|)×100<36
(9a) 0.15<|f2|/f<0.60
(10a) 0.2<|f3|/f<0.6
(11a) 16<νd3<29
(12a) 0.2<r1/f<0.3
(13a) 0.45<r1/|r2|<1.1
(14a) 0.25<|r2/r8|<1.50
(15a) 0.15<|r2/f1|<1.60
(16a) 1<|r3/r7|<3
(17a) 0.27<|r5|/f<0.65
(18a) 1.7<|r5|/T3<7.5
(19a) 0.10<|r5|/r6<1.35
(20a) 0.4<|r5/f3|<1.6
(21a) 0.3<r6/f<2.4
(22a) 0.2<|r7|/f<0.6
(23a) 0.4<|r7|/(T3+bf)<1.3
(24a) 0.2<|r7/r8|<1.3
(25a) 9<(D2/|f2|)×100<50
(26a) 0.1<|f2/f4|<0.6
However, the symbols of each conditional expression are the same as those described in the previous paragraph. Only the lower limit values or only the upper limit values of the conditional expressions (1a) to (26a) may be applied to the corresponding conditional expressions (1) to (26).

In this embodiment, the aspherical shape adopted for the aspherical surface of the lens surface has Z as the axis in the optical axis direction, H as the height in the direction perpendicular to the optical axis, R as the paraxial radius of curvature, k as the conic coefficient, When the aspherical coefficients are A4, A6, A8, A10, A12, A14, A16, A18 and A20, they are expressed by Equation 1.

Next, examples of the imaging lens according to the present embodiment will be shown. In each embodiment, f is the focal length of the entire imaging lens system, Fno is the F number, ω is the half angle of view, ih is the maximum image height, and TTL is the total optical length. In addition, i is the surface number counted from the object side, r is the paraxial radius of curvature, d is the distance between the lens surfaces on the optical axis (surface spacing), Nd is the refractive index of the d-line (reference wavelength), and νd is d The Abbe number for each line is shown. Aspherical surfaces are indicated by adding an asterisk (*) after the surface number i.

(Example 1)

Basic lens data is shown in Table 1 below.

The imaging lens of Example 1 achieves an F number of 3.80. Moreover, as shown in Table 7, the conditional expressions (1) to (26) are satisfied.

FIG. 2 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 1. FIG. The spherical aberration diagram shows the amount of aberration for each wavelength of the F-line (486 nm), d-line (588 nm), and C-line (656 nm). The astigmatism diagrams show the amount of d-line aberration (solid line) on the sagittal image plane S and the amount of d-line aberration (broken line) on the tangential image plane T (FIGS. 4, 6, and 8). , FIG. 10 and FIG. 12). As shown in FIG. 2, it can be seen that each aberration is well corrected.

(Example 2)

Basic lens data is shown in Table 2 below.

The imaging lens of Example 2 achieves an F number of 3.80. Moreover, as shown in Table 7, the conditional expressions (1) to (26) are satisfied.

FIG. 4 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 2. FIG. As shown in FIG. 4, each aberration is well corrected.

(Example 3)

Basic lens data is shown in Table 3 below.

The imaging lens of Example 3 achieves an F number of 3.80. Moreover, as shown in Table 7, the conditional expressions (1) to (26) are satisfied.

FIG. 6 shows spherical aberration (mm), astigmatism (mm), and distortion aberration (%) for the imaging lens of Example 3. FIG. As shown in FIG. 6, it can be seen that each aberration is well corrected.

(Example 4)

Basic lens data is shown in Table 4 below.

The imaging lens of Example 4 achieves an F number of 3.80. Moreover, as shown in Table 7, the conditional expressions (1) to (26) are satisfied.

FIG. 8 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 4. FIG. As shown in FIG. 8, each aberration is well corrected.

(Example 5)

Basic lens data is shown in Table 5 below.

The imaging lens of Example 5 achieves an F number of 3.80. Moreover, as shown in Table 7, the conditional expressions (1) to (26) are satisfied.

FIG. 10 shows spherical aberration (mm), astigmatism (mm), and distortion (%) for the imaging lens of Example 5. FIG. As shown in FIG. 10, each aberration is well corrected.

(Example 6)

Basic lens data is shown in Table 6 below.

The imaging lens of Example 6 achieves an F number of 3.80. Moreover, as shown in Table 7, the conditional expressions (1) to (26) are satisfied.

FIG. 12 shows spherical aberration (mm), astigmatism (mm), and distortion (%) of the imaging lens of Example 6. FIG. As shown in FIG. 12, each aberration is well corrected.

Table 7 shows values of conditional expressions (1) to (26) according to Examples 1 to 6.

When the imaging lens according to the present invention is applied to a product having a camera function, it can contribute to lowering the F-number of the camera and improve its performance.

ST Aperture diaphragm L1 First lens L2 Second lens L3 Third lens L4 Fourth lens IR Filter IMG Imaging surface

Claims (7)

Arranged in order from the object side to the image side,
a first lens having positive refractive power;
a second lens;
a third lens;
and a fourth lens,
the first lens has a convex surface on the object side in paraxial;
the third lens has a paraxial concave surface on the image side;
An imaging lens that satisfies the following conditional expressions (1), (2), (3), and (4).
(1) 13<νd4<34
(2) 0.3<νd3/νd4<2.0
(3) 0.25<|r2/r3|<0.85
(4) 0.85<|f4|/f<3.85
however,
νd4: Abbe number for the d-line of the fourth lens νd3: Abbe number for the d-line of the third lens r2: Paraxial radius of curvature of the image-side surface of the first lens r3: The radius of curvature of the object-side surface of the second lens paraxial radius of curvature f4: focal length of the fourth lens f: focal length of the entire imaging lens system 2. The imaging lens according to claim 1, wherein the following conditional expression (5) is satisfied.
(5) 0.15<|r2|/f<0.55
however,
r2: the paraxial radius of curvature of the image-side surface of the first lens f: the focal length of the entire imaging lens system 2. The imaging lens according to claim 1, wherein the following conditional expression (6) is satisfied.
(6) 0.2<|r3|/f<1.2
however,
r3: paraxial radius of curvature of the object-side surface of the second lens f: focal length of the entire imaging lens system 2. The imaging lens according to claim 1, wherein the following conditional expression (8) is satisfied.
(8) 9<(D3/|f3|)×100<43
however,
D3: thickness of the third lens on the optical axis f3: focal length of the third lens 2. The imaging lens according to claim 1, wherein the following conditional expression (9) is satisfied.
(9) 0.1<|f2|/f<0.7
however,
f2: focal length of the second lens f: focal length of the whole imaging lens system The first lens has a biconvex shape in the paraxial direction,
The second lens has a paraxial biconcave shape and negative refractive power,
The third lens has a meniscus shape with a concave surface on the image side in the paraxial direction and has a positive refractive power,
2. The imaging lens according to claim 1, wherein the fourth lens has a meniscus shape with a convex surface on the image side in the paraxial direction and has a negative refractive power. The first lens has a meniscus shape with a convex surface on the object side in the paraxial direction,
The second lens has a biconvex shape and a positive refractive power in the paraxial region,
The third lens has a paraxial biconcave shape and negative refractive power,
2. The imaging lens according to claim 1, wherein the fourth lens has a meniscus shape with a concave surface on the image side in the paraxial direction and has a positive refractive power.

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